It has been common practice to line closures for containers with a laminated material having a layer of pulp mounted to a layer of aluminum foil by an intermediate wax layer. The laminated material also contains a layer of polyester film fixed by an adhesive to the foil, and a film of sealing material fixed by an adhesive to the polyester layer. The laminate is produced and shipped in roll form, which are die cut into discs, then mounted in the container cap with a hot melt adhesive or by a friction fit.
The resulting lined caps are torqued onto a container, like a bottle or jar, filled with a fluid or solid product. The capped container then is passed through a high frequency induction heating unit. During induction heating, the aluminum foil is heated to a temperature in excess of about 300.degree. F., which melts the wax in the layer between the pulp and aluminum foil. The sealing material is selected to match the material of construction of the container, and is heat welded or sealed to the rim of the container during induction heating. When the consumer removes the cap from the container, the pulp is removed with the cap, leaving the foil, polyester film, and sealing material on the container to provide evidence of tampering and to prevent leakage and contamination.
One such liner/seal combination is disclosed in Yousif U.S. Pat. No. 4,596,338. The liner/seal combination disclosed in that patent provides an air-permeable paper seal to overcome problems associated with pressure changes within the container due to changes in temperature. Another liner/seal combination is disclosed in Cain U.S. Pat. No. 5,712,042, which also discloses a paper layer as the seal.
Each prior art linear/seal combination contains several layers of laminates, wherein laminates forming the seal form a tamper-evident seal. However, the prior art combinations do not allow consumers to observe or inspect the contents of the container because the seals are not transparent. It would be desirable to provide a liner/seal combination that provides a transparent seal thereby allowing a consumer to observe or inspect the contents of the container before the tamper-evident seal is removed. The present invention is directed to such liner/seal combinations.